Some earth-shattering sleuthing from the WSJ: No one really knows how many albums Michael Jackson sold—certainly not 750 million. See, in the barbaric days before album sales were electronically reported to Nielsen SoundScan—1991—it was all guesswork.
Here's how messed up the Billboard rankings were in the pre-electronic days: It used rankings, not actual sales numbers, assumed all albums on the chart had equal spacing between them, no matter how big the gap really was. So, whether a number one album sold just 10 or 10,000 more copies than the number two album, it showed up the same. And on top of only tracking the US and Canada—so not worldwide figures—SoundScan has no data pre-1991.
For what it's worth, Sony and the RIAA peg Jackson's sales at 55 million, though Jackson's management says it's more like 100 million. And those numbers don't include the digital explosion over the last couple weeks. (He held 9 out of the top 10 albums on iTunes after his death.) Other mythical albums sales figures are a lie too, conflating songs and albums: The Beatles haven't sold a billion albums, AC/DC hasn't topped 200 million.
What a far cry from iTunes today: It not only tracks every song and album you buy, it tells you songs you might like based on what you buy after comparing it to what everybody else is buying, and songs you might wanna listen to based on what you already have. We have far too many numbers now. [WSJ]